Clinical Characteristics of Walnut Allergy and Evaluation of Cross-Reactivity between Walnut and Peanut in Children Under 4 Years of Age

Purpose: Walnut (WN) allergy in young children has rarely been reported in Asia. This study focused on the clinical characteristics of WN allergy, co-sensitization, and cross-reactivity between WN and peanut (PN) in young Korean children. Methods: This study was based on a data analysis of 22 patients, all under the age of 4 years, who were diagnosed with allergic disease at Ajou University Hospital from January 2009 to December 2010. They were suspected to have a WN allergy or needed a screening examination to exclude food allergy. Sera from all children were analyzed for PN-, WN-, and pine nut-specific immunoglobulin E (IgE) (ImmunoCAP). Clinical details, feeding, and familial history of patients were collected by medical history. Additionally, we produced WN, PN, and pine nut extracts, and sera were tested with an enzyme linked immunosorbentassay inhibition test. Results: The subjects were 16 male and 6 female with a median aged of 24 months. Ten of 22 had a definite history of WN exposure. Among them, two (4.28 kU/L, 11.1 kU/L) were diagnosed with anaphylaxis, four (7.34 to 27.4 kU/L) were diagnosed with angioedema, and four (1.35 to 3.17 kU/L) were diagnosed with urticaria. We confirmed that PN in the IgE-ELISA was profoundly inhibited by the WN extract. Conclusion: This study identified multiple cases of WN allergy in young children in Korea, indicating that it is not rare. Co-sensitization and clinical adverse reactions between PN and WN suggests that more investigations are needed to conclude cross-reactivity between PN and WN. (Pediatr Allergy Respir Dis(Korea) 2011;21:261-268)